Magazine article Clinical Psychiatry News

Surgeon General: No Smoke Is Safe Smoke: Evidence Exists to Infer Causal Relationship between Secondhand Exposure, Lung Cancer in Nonsmokers

Magazine article Clinical Psychiatry News

Surgeon General: No Smoke Is Safe Smoke: Evidence Exists to Infer Causal Relationship between Secondhand Exposure, Lung Cancer in Nonsmokers

Article excerpt

The science is now anything but hazy: Secondhand tobacco smoke causes premature death and disease in children and adults who don't smoke--and there is no safe exposure level, the U.S. surgeon general warned in a comprehensive new report.

In a return to a public health issue last addressed in a 1986 surgeon general's report, the nation's top physician found significant progress in the campaign to reduce Americans' exposure to secondhand smoke. But new scientific evidence in the intervening 20 years strengthens the links between involuntary smoking and a host of harmful cardiovascular, respiratory, and reproductive effects.

In particular, the surgeon general's report cautioned that exposure to secondhand smoke increases nonsmokers' risk of developing heart disease by 25%-30% and lung cancer by 20%-30%.

In addition, the home is surpassing work as the primary source of secondhand smoke exposure--a trend that poses special danger for children, who are at increased risk for sudden infant death syndrome, ear problems, asthma, and acute respiratory infections. As a result, physicians "should routinely ask about secondhand smoke exposure, particularly in susceptible groups or when a child has an illness caused by secondhand smoke, such as pneumonia," U.S. Surgeon General Richard H. Carmona said in his 709-page review, "The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General."

Clearing the Air

The new report acknowledges that the secondhand smoke picture has cleared significantly since the last look at the topic 20 years ago. Thanks to the spread of smoke-free environments at work sites and other public places, levels of cotinine, a biologic marker for secondhand smoke exposure, have fallen in nonsmokers by 70% since the late 1980s. The proportion of nonsmokers with detectable cotinine levels has been halved from 88% in 1988-1991 to 43% in 2001-2002.

Nonetheless, nearly half of all nonsmoking Americans are still regularly exposed to secondhand smoke, and children's median cotinine levels were more than twice those of adult nonsmokers.

The California Environmental Protection Agency highlighted secondhand smoke's human toll in a 2005 study cited by the U.S. surgeon general. Exposure resulted in an estimated 3,400 deaths annually from lung cancer, 46,000 deaths from cardiac-related illnesses, and 430 deaths from sudden infant death syndrome.

More than 50 carcinogens have been identified in sidestream and secondhand smoke, and there is sufficient evidence that exposure in nonsmokers cause a "significant increase" in urinary levels of metabolites of the tobacco-specific lung carcinogen NNK, or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

The Cardiorespiratory Costs

Two decades of new data further cement the causal links connecting secondhand smoke to cardiovascular and respiratory disease. Sufficient evidence now exists to infer a causal relationship between secondhand smoke exposure and lung cancer in lifetime nonsmokers--a conclusion that extended to all secondhand smoke exposure, regardless of location. The data supporting a causal link between exposure and breast cancer are suggestive but not sufficient.

The evidence is sufficient to back a causal link between secondhand smoke and increased risk of coronary heart disease, although the report deemed the evidence of increased risk of stroke or atherosclerosis as "suggestive but not sufficient."

Among people with asthma, the evidence is suggestive but is not sufficient to infer a causal relationship between secondhand smoke exposure and acute respiratory symptoms such as cough, wheeze, chest tightness, and difficulty breathing. …

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